EUVD-2026-41445
GHSA-6xf4-794h-3f7w
Severity by source
AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Network-delivered open redirect needs no attacker auth (PR:N) but requires the victim to click (UI:R); token leakage across trust boundary yields S:C with C:H/I:H and no availability impact (A:N).
Primary rating from Vendor (microsoft).
CVSS VectorNVD
Lifecycle Timeline
2DescriptionNVD
Url redirection to untrusted site ('open redirect') in M365 Copilot allows an unauthorized attacker to elevate privileges over a network.
AnalysisAI
Privilege elevation in Microsoft 365 Copilot arises from an open redirect (CWE-601) that lets an unauthenticated remote attacker craft a Copilot-hosted URL that forwards a victim to an attacker-controlled site. Per the CVSS vector this requires the victim to interact (UI:R) with the malicious link and results in a scope change with high confidentiality and integrity impact, consistent with token/credential capture enabling elevated access. There is no public exploit identified at time of analysis (Exploit Maturity: Unproven), and it is not listed in CISA KEV; Microsoft rates it 9.3 and reports an official fix is available.
Technical ContextAI
The affected component is Microsoft 365 Copilot (cpe:2.3:a:microsoft:microsoft_365_copilot), Microsoft's cloud-hosted generative-AI assistant integrated across Microsoft 365 services. The root cause is CWE-601, URL Redirection to an Untrusted Site ('Open Redirect'): a Copilot endpoint accepts a user- or attacker-supplied destination parameter and issues a redirect without validating it against an allowlist of trusted domains. Because Copilot links carry the trust of the microsoft.com/office ecosystem and often flow alongside authenticated sessions and OAuth-style token exchanges, an open redirect can be abused to leak authorization material or land a victim on a convincing phishing/consent page, which is why Microsoft characterizes the outcome as elevation of privilege rather than a simple redirect nuisance.
RemediationAI
Patch available per vendor advisory - as a Microsoft-operated cloud service, the fix is applied server-side by Microsoft, so no customer-side upgrade action is generally required; confirm your tenant is current and consult the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41106 for any tenant-specific guidance. As compensating controls while validating that the fix has reached your tenant, reinforce user-facing phishing defenses: enable and tune Safe Links/URL detonation in Microsoft Defender for Office 365 to inspect and rewrite Copilot-originated links (trade-off: slight added latency on link click), warn users against following unexpected Copilot or Office share links, and review conditional access and OAuth app-consent policies to limit what a hijacked or redirected session can escalate to (trade-off: stricter consent policies may block some legitimate third-party integrations). No exact fix version is published for a SaaS deployment, so do not rely on a version check - rely on the vendor advisory status.
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